JPH06291346A - Photoelectromotive force device - Google Patents

Abstract

PURPOSE:To enhance photoelectric conversion efficiency by using an insulation layer comprising resin and a spacer between transparent electrodes. CONSTITUTION:An aluminum electrode 100, an n type polycrystalline silicon 101, a p type polycrystalline silicon 102, an ITO transparent electrode 103, an insulation layer 104, an ITO transparent electrode 105, an n type amorphous silicon 106, an I type amorphous silicon 7, a p type amorphous silicon 108, a transparent electrode 109 and a permeable protection layer 110 are formed one after another, thereby producing tandem structure between a pn junction cell of polycrystal silicon and a pin junction cell of amorphous silicon. As for the insulation layer 104, it is more preferable to use resin whose refractive index is 1.64 and more and 2.00 and below and whose thermosoftening temperature exceeds 80 deg.C. It is also advisable to use a spacer having a refractive index closer to that of the resin in order to a constant thickness. This construction makes it possible to enhance the reliability of elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device having a plurality of photoelectric conversion regions for directly converting light energy into electric energy.

[0002]

2. Description of the Related Art As a means for solving energy problems such as a decrease in fossil fuel reserves and an increase in mining costs, and a global environmental problem due to combustion of fossil fuels, solar cells that generate electricity using solar energy are Attention has been paid.

However, at present, the power generation cost is higher than that of power generation methods such as nuclear power, thermal power, and hydraulic power, and it is necessary to reduce the power generation cost for the spread of solar cells.

In order to reduce the power generation cost, it is effective to generate more electric energy when the same amount of light energy is received in the same area, that is, to increase the photoelectric conversion efficiency.

Therefore, several methods for increasing the photoelectric conversion efficiency of the solar cell have been devised. For example, JP-A-59
As disclosed in JP-A-124772 and JP-A-3-19374, in order to efficiently convert the energy of incident light into electric energy, a tandem solar cell in which a plurality of semiconductors having different band gaps are combined has been proposed. There is.

[0006]

However, in the tandem type solar cells shown in these proposals, the two-terminal type solar cell as shown in FIG. 2 has two semiconductors connected in series. Precise film thickness control is required, and when the balance of the output current is lost, the output sharply decreases, which is not preferable in terms of reliability.

The four-terminal type as shown in FIG. 3 is highly reliable but requires an insulating layer between transparent electrodes (1 in FIGS. 2 and 3 is a transparent substrate, 2 is a transparent substrate). Is a transparent electrode,
3 is a p-type semiconductor, 4 is an i-type semiconductor, 5 is an n-type semiconductor, 6
Is a transparent electrode, 7 is a p-type semiconductor, 8 is an n-type semiconductor, 9 is a back electrode, 10 is an insulating layer, and 11 is a transparent electrode).

At present, a resin such as polyimide used as a sealing material is used as a material for the insulating layer.

However, in this case, the resin applied to the insulating layer may be softened by the heat applied during the semiconductor manufacturing process, and the electrodes may come into contact with each other (short-circuit), so that the reliability of the device cannot be maintained. .

Further, when a plurality of semiconductors are formed and then joined with a resin, they are not exposed to the high temperature as in the semiconductor formation, but they are used for a long period of time or due to an unexpected force from the outside. There is a problem that the electrodes contact each other.

Further, when the thickness of the insulating layer reaches the wavelength level of light, there is a problem that light interference occurs, the light cannot be effectively used, and the photoelectric conversion efficiency decreases.

The present invention is intended to solve the above-mentioned drawbacks of the prior art, and an object thereof is to provide a highly reliable photovoltaic element.

[0013]

In order to achieve the above-mentioned object of the present invention, it has the following constitution.

[In a photovoltaic element formed by joining a plurality of photovoltaic elements having a semiconductor bonding surface, an insulating layer composed of a resin and a spacer is used as an insulating layer used between transparent electrodes on the semiconductor bonding surface. Photovoltaic device characterized by the above. ”The inventors of the present invention believe that the problems in the above-mentioned conventional technology are caused by the fact that the insulating layer between the transparent electrodes is an organic substance and is softened or partially decomposed by heat. It has been found that the reliability is improved by the presence of the spacer which is not easily deformed by heat in the resin used as the insulating layer.

Further, in order to obtain high photoelectric conversion efficiency,
It has been found that the spacer is effective for securing the thickness of the insulating layer (the distance between the transparent electrodes) or for keeping the thickness constant.

It is preferable that the spacer is less susceptible to thermal deformation.

For example, fine particles of a resin having a crosslinked structure, inorganic fine particles and inorganic fibers are preferable, and as the fine particles of a resin having a crosslinked structure, a compound having two or more polymerization functional groups in the molecule such as divinylbenzene is used. Examples thereof include fine particles obtained by polymerizing the contained monomer composition.
Above all, 1 to 50% by weight of divinylbenzene / 5 styrene
Fine particles obtained by copolymerization at 0 to 99% by weight are preferable.

As the inorganic fine particles or the inorganic fibers, glass fine particles or glass fibers are preferable in terms of transparency.

Further, in order to increase the conversion efficiency and to reduce the reflection at the interface between the transparent electrode and the insulating layer, it is preferable that the material used for the insulating layer and the transparent electrode have a refractive index as close as possible.

The resin used for the insulating layer is not particularly limited, but has a refractive index nd of 1.64 or more,
A resin of 2.00 or less is particularly preferably used.

More preferably, the refractive index is 1.70 or more,
A resin of 2.00 or less is suitable. Further, from the viewpoint of reliability in use, it is preferable to use a resin having a thermal softening temperature of 80 ° C or higher.

In this case, the above-mentioned spacer is preferably a spacer having a refractive index closer to that of the resin used for the insulating layer.

As such a spacer, glass particles or glass fibers made of high refractive index glass are preferable.
As the high refractive index glass, one having a refractive index close to that of a resin is preferable, and flint glass obtained by adding a metal compound such as lead oxide or titanium oxide to ordinary glass is generally used.

A method for manufacturing a device according to the present invention will be described.

When the side on which light enters through the insulating layer is the upper cell and the opposite side where the back electrode is provided is the lower cell,
The easiest method is to manufacture the upper cell and the lower cell and then bond them with a resin containing a spacer.

However, when this method is used, two substrates for forming a semiconductor are required, which is inefficient.

Therefore, as a preferred method, after providing a semiconductor layer and a transparent electrode constituting an upper cell on a transparent substrate (glass substrate, sapphire substrate or resin film substrate), an insulating layer (spacer + resin) is provided, There is a method of providing a transparent electrode, a semiconductor layer, and a back surface electrode which compose the lower cell on it.

In addition, an insulating layer (spacer + resin) is provided on the substrate (metal substrate, glass substrate, sapphire substrate, resin film substrate) after providing the back electrode, semiconductor layer, and transparent electrode constituting the lower cell. You may use the method of providing the semiconductor layer and transparent electrode which comprise an upper cell on it.

However, when an amorphous semiconductor is used for the upper cell, the former method is preferable because it is not necessary to provide a protective layer.

The resin used for the insulating layer is not particularly limited, but its components include a sulfur atom,
The total content of bromine atom, benzene ring and naphthalene ring is 3
It is preferable to use a resin of 0% by weight or more, and more specifically, a resin having the following structure is preferable.

[0031]

[Chemical 1] In the above structure, X represents Cl, bromine or iodine. n is an integer of 1 to 5 and m is an integer of 1 to 4.

As a method of forming an insulating layer with a resin, a method of sticking a resin film or a monomer composition (a monomer unit of the resin or an oligomer obtained by polymerizing several to several hundred monomer units) which is a raw material of the resin is used. Then, a composition containing a polymerization initiator (catalyst) as a main component) is applied on the prepared cell, and then heat is applied or energy rays such as ultraviolet rays and X-rays are irradiated to perform polymerization. To be

More preferably, the monomer used has the following structural formula.

[0034]

[Chemical 2]

[Chemical 3] Further, it is preferable to use a compound corresponding to the polymerization functional group as the initiator, and for the monomer having a double bond in the molecule, a known radical polymerization initiator, anionic polymerization initiator, or cationic polymerization initiator is used. To be

When thermal polymerization is carried out, radical polymerization is preferably used because process control is easy. In this case, the radical polymerization initiator is generally a peroxide-based initiator or an azo-based initiator. Initiators can be used.

Various kinds of compounds can be used as an example of a specific compound.

For example, benzyl peroxide, di-i
so-propyl peroxycarbonate, di-iso-
Propyl peroxydicarbonate, di-2-ethylhexyl peroxydicarbonate, di-n-propyl peroxydicarbonate, t-butyl peroxy-2-
Hexyl hexanate, azobisisobutyronitrile and the like can be mentioned.

This resin preferably has a strong adhesive force with the transparent electrode in order to endure long-term use.

A strong adhesive force can be obtained by using a compound that enhances the adhesive force particularly as a component of the monomer composition applied to increase the adhesive force.

The compound for increasing the adhesive strength is not particularly limited as long as it is a compound generally used as an adhesive, but urea resin, melamine resin, phenol resin, epoxy resin, urethane, At least one of thiol urethane-based, acrylic-based, thiol-acrylic-based, and silicone resin-based adhesives is added to the monomer composition in a proportion of 0.01 to 40% by weight, so that the resin is resinized. The adhesiveness with the transparent electrode is increased.

However, since these lower the refractive index of the insulating layer, it is preferable to add them in a proportion of 0.01 to 5% by weight.

Further, it is effective to add glycidyl (meth) acrylate or cyanoacrylate in a proportion of 0.01 to 5% by weight because the adhesive strength with an inorganic substance is increased.

In the present invention, the semiconductor constituting the semiconductor junction surface used for the upper cell and the lower cell may be an amorphous semiconductor, a microcrystal semiconductor, a polycrystal semiconductor, a single crystal semiconductor, or a known compound semiconductor. It is essential that the band gap of the semiconductor used for the upper cell is larger than the band gap of the semiconductor used for the lower cell.

This is because the lower cell effectively absorbs the light not absorbed by the upper cell.

As a preferable combination used in this case, an amorphous semiconductor, especially an amorphous silicon (a-Si) semiconductor, a hydrogenated amorphous silicon (a-Si) is generally used as a semiconductor having a wide band gap in the upper cell. / H) semiconductor and an amorphous silicon germanium (a-Si _m Ge _n ) semiconductor are preferably used as the semiconductor junction region.

On the other hand, as a semiconductor used for the lower cell semiconductor junction region, amorphous silicon germanium (a-Si _m Ge _n ) is used as a semiconductor having a narrow band gap.
A semiconductor or a crystalline semiconductor (microcrystal semiconductor, polycrystal semiconductor, single crystal semiconductor) is preferably used, but a crystalline semiconductor (microcrystal semiconductor, polycrystal semiconductor, single crystal semiconductor) is preferable from the viewpoint of absorption efficiency, It is more preferable to use a microcrystal semiconductor or a polycrystal semiconductor from the viewpoint of cost.

Further, when forming a junction surface of these semiconductors, it is not necessary to use the same material for the p layer and the n layer. For example, the p layer can be an amorphous semiconductor and the n layer can be a crystalline semiconductor.

Furthermore, it is also possible to join an amorphous semiconductor and a crystalline semiconductor as a p-layer or an n-layer of the same cell.

In addition to the photovoltaic element (tandem type) including two cells, the method of the present invention can enhance the performance of a multi-stage multi-layer type photovoltaic element including three or more cells.

[0050]

EXAMPLES The present invention will be described with reference to examples.

The present invention is not limited to this embodiment.

Example 1 FIG. 1 is a schematic drawing showing Example 1 of the electromotive element of the present invention.

As shown in the drawing, the aluminum electrodes 100, n
Type polycrystalline silicon 101, p type polycrystalline silicon 102,
ITO transparent electrode 103, insulating layer 104, ITO transparent electrode 105, n-type amorphous silicon 106, i-type amorphous silicon 107, p-type amorphous silicon 10
8, a transparent electrode 109, and a translucent protective layer 110 are formed in this order to form a tandem structure of a pn junction cell of polycrystalline silicon and a pin junction cell of amorphous silicon.

As a manufacturing method, a pn junction cell made of polycrystalline silicon formed on an aluminum electrode is prepared, and separately from this, an IT formed on a glass substrate by a sputtering method.
O transparent electrode and pin formed by plasma CVD
A pin cell having an amorphous silicon layer is prepared, and 80 parts by weight of a compound having a structure represented by the following formula (A), 17.5 parts by weight of styrene, and 1.0% of glycidyl methacrylate are provided on the transparent electrode side of the cell of polycrystalline silicon. 50 parts by weight, after spin-coating a monomer composition containing 1.0 part by weight of glass fiber made of flint glass containing lead oxide and having a refractive index of nd 1.70 and 0.5 part by weight of benzoyl peroxide. A tandem solar cell obtained by heating at ℃ for 2 hours, AM1.5, 100mW / c
The photoelectric conversion efficiency when irradiated with m ² standard sunlight is 1
It was 7.5%.

[0055]

[Chemical 4] Comparative Example 1 Instead of the monomer composition used in Example 1, 80 parts by weight of a compound having the structure represented by the above formula (A), 18.5 parts by weight of styrene, 1.0 part by weight of glycidyl methacrylate, and benzoylper. AM was applied to a tandem solar cell obtained by spin-coating a monomer composition containing 0.5 part by weight of oxide and then heating at 50 ° C. to 120 ° C. for 2 hours.
The photoelectric conversion efficiency when irradiated with standard sunlight of 1.5 and 100 mW / cm ² was 17.0%.

[0056]

According to the present invention, the reliability of the device can be improved.

[Brief description of drawings]

FIG. 1 shows a tandem structure in Example 1 of the present invention.

FIG. 2 is a schematic cross-sectional view of a two-terminal tandem solar cell in a conventional example.

FIG. 3 is a schematic cross-sectional view of a 4-terminal tandem solar cell in a conventional example.

[Explanation of symbols]

 100: Aluminum electrode 101: n-type polycrystalline silicon 101 102: p-type polycrystalline silicon 103: ITO transparent electrode 104: insulating layer 105: ITO transparent electrode 106: n-type amorphous silicon 107: i-type amorphous silicon 108: p-type Amorphous silicon 109: Transparent electrode 110: Translucent protective layer

Claims (4)

[Claims] 1. A photovoltaic element formed by joining a plurality of photovoltaic elements having a semiconductor bonding surface, wherein an insulating layer made of a resin and a spacer is used as an insulating layer used between transparent electrodes on the semiconductor bonding surface. Photovoltaic device characterized by the above. 2. The photovoltaic element according to claim 1, wherein an inorganic material such as glass fiber is used as the spacer. 3. The resin used for the insulating layer has a refractive index nd.
Is 1.64 or more and 2.00 or less, and a resin having a thermal softening temperature of 80 ° C. or more is used, and the photovoltaic element according to claim 1. 4. When the refractive index of the resin used for the insulating layer is N, the refractive index of the material used as the spacer is N ± 0.
The photovoltaic element according to claim 1, wherein the photovoltaic element is 05.